Since the usage of mobile phones, PDAs, or palm games become more popular day after day. In order to maintain safety driving, many countries have prohibited drivers from using mobile phones, PDAs, or palm games when driving a car. Further, the power supply of a car is used for supplying power and charging a battery when these appliances are used in the car. To concurrently meet the requirements for convenience and safety, an automobile usually is equipped with a battery charger or hand-free clamping holder. Further, there are different types and specifications of the sockets, but the battery chargers or hand-free clamping holders are designed for single model only and thus are applicable to a specific model or a specific type of electronic appliances. Besides the costs, such arrangement also occupies space and cause confusions. When a different electronic appliance or a different model is used, it usually requires to buy new battery chargers or hand-free clamping holders again. Let us assume there are several tens of manufacturers, and each has several different models of connectors. Furthermore, these appliances have a short life cycle, and new models are coming out constantly, and users keep buying them. It is a waste to keep buying and throwing away different adapters and clamping holders repeatedly. Such arrangement also causes inconvenience and trouble to manufacturing for the inventory and storage. In addition, it is inconvenient for users to carry many different sets of clamping holders in a car for the use of an electronic appliance such as a mobile phone, a PDA, or a palm game. Both inconvenience and increased cost are the major subjects that deserve immediate improvements.